LOAD BALANCING OF SINGLE STAGE STEAM TURBINES BY USING TANDEM GENERATORS TO INCREASE ELECTRICAL OUTPUT BY 100%

Ziel

To demonstrate an economic technique for increasing the power output and efficiency of steam turbine driven power generators, which have been sized for a single load condition. The technique applies to back pressure turbine CHP systems which rely on minimum process loads to guarantee power production.
The range of process loads, over which power can be generated and efficiency of generation increased, is widened by the integration of a second set of turbines coupled to a variable condenser.
The new installation will boost the power generation by 100% without further investment in boiler plant. The power ratio of the tandem turbines will be increased from 2.8 to 3.5.L%
The installation first entered normal service on 5th April 1993, following a four weeks commissioning period. The plant has operated throughout the year for 6000 hours. There have been 4 periods without generation as follows :
(i) 400 hours were lost while the generator bushes on the excitor were replaced.
(ii) 600 hours were lost due to a voltage cabling fault on the original turbine set N0.1.
(iii) 1500 hours shutdown for annual site maintenance.
(iv) 200 hours periodic stoppages.
The anticipated normal operational period would be 8000 hours/annum.
The new tandem generating set now forms an integral part of the existing CHP Plant to maximise on the potential electrical power generation with varying steam loads.
From the full output of the boiler plant, a total of almost 3 MW of power is generated. This is based on 37% of the total steam generated passing through the new turbines. With a full process steam demand, the maximum output is reduced to 2.2 MW. The system has been designed to maintain the optimum efficiency from the existing primary tandem generating set by increasing the steam demand during low production process requirement.
The control system maintains the electrical power output at 1800-2200 kW during high steam demands, above 15 tonnes/hour to the process. When the process requirement falls below 12 tonnes/hour, the electrical power output remains above 600 kW.
Over 8,6 million kWhs have been generated for the 6000 operational hours during the initial 12 months monitoring period. This is lower than the projected generation of 15,8 million kWh, however, the potential during the 1993/1994 season was not there due to reduced production and subsequent lower process steam demand. The projected electrical generation was based on the 1989/1990 process steam load of 160,000 tonnes. By allowing for the reduced process steam demand and operational hours, the total installation would have generated in excess of 15 million kWh.
During the 12 months monitoring period, the total fuel oil consumption for steam raising was 13287 tonnes. The quantity relates to a total process steam loading of 120,000 tonnes.
The basis for comparison on the electrical performance and economics is the same period for the previous season 1992/1993. A summary on the technical performance of the new and old configurations are as follows :
OIL CONSUMPTION POWER GENERATION STEAM TO PROCESS
(TONNES) (kWh) (TONNES)
1993/94 13,287 8,623,890 120,656
Monitoring period
1992/93 9,476 3,127,885 96,101
Difference 3,811 5,496,005 24,555
The process steam requirement has increased by 25.55% for 1993/1994 over 1992/1993. The extra oil consumption necessary to satisfy this additional loading would be 2421 tonnes.
Based on the increased steam demand, the additional oil consumption to generate 5,496,005 kWh of electricity was 1390 tonnes.
A tandem turbine is already in place and operating at Waterford Foods. At low steam demands, below 17 tonnes/hour, power is no longer generated and the boiler operates on part load.
The installation of a second tandem turbine set operating between the process steam condition and a variable condenser will improve the overall power generation facility. One of the turbines in this new tandem set will use the steam feed to the deaerator as the driver. This has the effect of keeping the new generator and tandem steam turbine in spinning reverse. As the process steam load drops, low pressure steam will be diverted to the new tandem set to generate power. In doing this the steam flow through the existing high pressure turbine set is maintained and power continues to be generated at high efficiency.
The new installation is to take 3.33 Kg/sec (11.88 tonnes/hr) from the 11 bar discharge of the existing tandem turbine set. The new tandem set will have one turbine passing steam to a modulating condenser and the other being supplied by the deaerator steam which is reduced to 1.4 bar.
The deaerator steam flow is a constant 1.1 Kg/sec which represents 11% of the maximum steam flow of 9.95 kg/sec (36 tonnes/hr). Normally 8% of the steam flow goes through the deaerator, however, in this case, a steam flow increase to 1.1 kg/sec is required to generate a mechanical output of 237 kW which will at all times keep the tandem set on line.
This second tandem turbine will generate 837 kW and will pass steam to a modulating condenser. The maximum steam flow will be 2.2 kg/sec and vary from zero upwards. The condenser will modulate to ensure there is always a minimum load of 5.5 kg/sec (20 tonnes/hr) feeding across the existing tandem turbine set which with the addition of the second tandem set will generate a total of 2 MW.

Programm/Programme

ENG-THERMIE 1 - Programme (EEC) for the promotion of energy technology in Europe (THERMIE), 1990-1994

Thema/Themen

2.3 - INDUSTRY

Aufforderung zur Vorschlagseinreichung

Data not available

Finanzierungsplan

DEM - Demonstration contracts

Koordinator

WATERFORD FOODS PLC

EU-Beitrag

Keine Daten

Adresse

BRIDGE HOUSE DUNGARVAN
CO Waterford
Irland

Gesamtkosten